<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for="(item, index) in arr" :key="index">
        {{ item.name }}
        <button @click="add(index)">买书</button>
      </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
      <tr v-for="(item, index) in arr" :key="index">
        <td>{{ index + 1 }}</td>
        <td>{{ item.name }}</td>
        <td>{{ item.price }}</td>
        <td>{{ item.count }}</td>
        <td>{{ item.sum }}</td>
      </tr>
    </table>
    <p>总价格为: {{ total }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
          sum: 0
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
          sum: 0
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
          sum: 0
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
          sum: 0
        },
      ],
      
    };
  },
  methods: {
    add(index) {
      this.arr[index].count++
      this.arr[index].sum = this.arr[index].count * this.arr[index].price
    }
  },
  computed: {
    total() {
      let totalAll = 0
      this.arr.forEach(item =>  totalAll += item.sum)
      return totalAll
    }
  }
};
</script>